Prospects for Detecting Gamma Rays from Annihilating Dark Matter in Dwarf Galaxies in the Era of DES and LSST

Among the most stringent constraints on the dark matter annihilation cross section are those derived from observations of dwarf galaxies by the Fermi Gamma-Ray Space Telescope. As current (e.g., Dark Energy Survey, DES) and future (Large Synoptic Survey Telescope, LSST) optical imaging surveys discover more of the Milky Ways ultra-faint satellite galaxies, they may increase Fermis sensitivity to dark matter annihilations. In this study, we use a semi-analytic model of the Milky Ways satellite population to predict the characteristics of the dwarfs likely to be discovered by DES and LSST, and project how these discoveries will impact Fermis sensitivity to dark matter. While we find that modest improvements are likely, the dwarf galaxies discovered by DES and LSST are unlikely to increase Fermis sensitivity by more than a factor of ~2-4. However, this outlook may be conservative, given that our model underpredicts the number of ultra-faint galaxies with large potential annihilation signals actually discovered in the Sloan Digital Sky Survey. Our simulation-based approach focusing on the Milky Way satellite population demographics complements existing empirically-based estimates.